Golf club head with face wall flexure control system

ABSTRACT

A metal club head designed for increased flexure at ball impact including a face wall reinforcing network that increases in thickness from the perimeter wall to a point near the face wall geometric center.

RELATED APPLICATION

[0001] This application is a Continuation in Part of U.S. applicationSer. No. 09/344,172, Filed: Jun. 24, 1999, entitled “GOLF CLUB FACEFLEXURE CONTROL SYSTEM” filed in the name of Dillis V. Allen, and isrelated to U.S. application Ser. No. ______, Filed: ______, entitled“IMPROVED GOLF CLUB HEAD WITH FACE WALL FLEXURE CONTROL SYSTEM”.

BACKGROUND OF THE INVENTION

[0002] In the last several years, the USGA has struggled with attemptingto devise a fair test to limit the trampoline effect of the face wall atball impact. Recent innovation in titanium alloys, and particularly theBeta titanium alloys has enabled the golf club head designer todramatically reduce face thickness and achieve greater face flexurewithout face failure. Faced with the politics of golf integrity, whichpits the golf traditionalists against those seeking enhanced performancefrom new technology, the USGA has devised a rebound test where a ball isfired at a test sample club and inlet and outlet velocities aremeasured. If ball exit velocities exceed the inlet velocity by apredetermined fractional multiplica (<.90) not relevant to thisdiscussion, the club fails the test. There is also a great debate as towhether such USGA testing is in the best interest of golf, particularlyfor amateur players, who Arnold Palmer characterizes as a group thatshould not be bound by these strict USGA rules, but should be permitteduse of clubs that do not conform to the present (July 2001) USGA testingrules.

[0003] In any event, the USGA rules and the concomitant colossal debateover which clubs are legal and which are not has created a large marketfor both clubs that marginally pass the USGA rules and those that areillegal under the USGA rules. The latter market is enhanced because theUSGA rules are not applicable outside North America.

[0004] In this environment, the present invention is directed toward aplurality of techniques for increasing the flexure of the face wall of agolf club without exceeding the elastic limit anywhere across the facewall. Conventional techniques for varying face wall flexure are: (1)face wall material selection; (2) face wall shape variation; (3) facewall area control; (4) face wall heat treatment, and, of course; (5)face wall thickness changes.

[0005] By using trial and error techniques, many golf club headdesigners have combined these factors to achieve what is now termed a“non-conforming” club head. Several manufacturers including CallawayGolf and Ping Golf, as well as many of their imitators, have a variablethickness face wall where the face is thicker near the point of ballimpact and thins as it approaches the perimeter wall. The problem withthis technique is the thickness of the face must be over 0.125 inchesover a major portion of the face wall to prevent face wall failure, andface thickness variation is limited to 2× because of club head weightlimitations. The present invention solves these problems.

[0006] Investment casting techniques innovated in the late 1960s haverevolutionized the design, construction and performance of golf clubheads up to the present time. Initially only novelty putters and ironswere investment cast, and it was only until the early years of the 1980sthat investment cast metal woods achieved any degree of commercialsuccess. The initial iron club heads that were investment cast in thevery late 1960s and early 1970s innovated the cavity backed club headsmade possible by investment casting which enabled the molder and tooldesigner to form rather severe surface changes in the tooling that werenot possible in prior manufacturing techniques for irons which werepredominantly at that time forgings. The forging technology wasexpensive because of the repetition of forging impacts and the necessityfor progressive tooling that rendered the forging process considerablymore expensive than the investment casting process and that distinctionis true today although there have been recent techniques in forgingtechnology to increase the severity of surface contours albeit them atconsiderable expense.

[0007] The investment casting process, sometimes known as the lost waxprocess, permits the casting of complex shapes found beneficial in golfclub technology, because the ceramic material of the mold is formed bydipping a wax master impression repeatedly into a ceramic slurry withdrying periods in-between and with a silica coating that permitsundercutting and abrupt surface changes almost without limitation sincethe wax is melted from the interior of the ceramic mold after completehardening.

[0008] This process was adopted in the 1980s to manufacture “wooden”club heads and was found particularly successful because theconstruction of these heads requires interior undercuts and thin wallsbecause of their stainless steel construction. The metal wood club head,in order to conform to commonly acceptable club head weights on theorder of 195 to 210 gms. when constructed of stainless steel, must haveextremely thin wall thicknesses on the order of 0.020 to 0.070 inches onthe perimeter walls to a maximum of 0.125 inches on the forward wallwhich is the ball striking surface. This ball striking surface, evenutilizing a high strength stainless steel such as 17-4, withoutreinforcement, must have a thickness of at least 0.125 inches tomaintain its structural integrity for the high club head speed player oftoday who not uncommonly has speeds in the range of 100 to 150 feet persecond at ball impact.

[0009] Faced with this dilemma of manufacturing a club head of adequatestrength while limiting the weight of the club head in a driving metalwood in the range of 195 to 210 gms., designers have found it difficultto increase the perimeter weighting effect of the club head.

[0010] Metal woods by definition are perimeter weighted because in orderto achieve the weight limitation of the club head described above withstainless steel materials, it is necessary to construct the walls of theclub head very thin which necessarily produces a shell-type constructionwhere the rearwardly extending wall extends from the perimeter of theforward ball striking wall, and this results in an inherently perimeterweighted club, not by design but by a logical requirement.

[0011] Prior attempts to manufacture very large stainless steel metalclub heads with larger than normal faces has proved exceedinglydifficult because of the 195 to 210 gm. weight requirements for drivingclub heads to achieve the most desirable club swing weights. Thus, tothe present date stainless steel “jumbo” club heads have beenmanufactured with standard sized face walls, deeply descending top wallsfrom the front to the rear of the club head, and angular faceted soleplates all designed to decrease the gross enclosed volume of the headbut which do not detract from the apparent, not actual, volumetric sizeof the head. This has led to many manufacturers switching from stainlesssteel to aluminum and titanium alloys, which are of course lighter, toenlarge the head as well as the face.

[0012] A further problem in the prior art references which suggestutilizing these rigidifying elements, is that they are completely silenton how these reinforcing elements, when not cast into the face wall, areattached into the club head. And the method of attachment, as will beseen from the present invention, is critical to the benefits ofincreasing resonant frequency and rebound of the face wall in accordancewith the present invention. Presently known bonding techniques are notsufficient to yield these benefits.

[0013] Still another of these prior references suggests making the headof synthetic material and the support rod of a similar material, butthese low modulus and soft materials cannot significantly raise theresonant frequency or rebound time of the ball striking face wall.

[0014] The following patents or specifications disclose club headscontaining face reinforcing elements:

[0015] Foreign Patents:

[0016] British Patent Specification, No. 398,643, to Squire, issued Sep.21, 1933;

[0017] United States Patents:

[0018] Clark, U.S. Pat. No. 769,939, issued Sep. 13, 1904

[0019] Palmer, U.S. Pat. No. 1,167,106, issued Jan. 4, 1916

[0020] Barnes, U.S. Pat. No. 1,546,612, issued Jul. 21, 1925

[0021] Drevitson, U.S. Pat. No. 1,678,637, issued Jul. 31, 1928

[0022] Weiskoff, U.S. Pat. No. 1,907,134, issued May 2, 1933

[0023] Schaffer, U.S. Pat. No. 2,460,435, issued Feb. 1, 1949

[0024] Chancellor, U.S. Pat. No. 3,589,731, issued Jun. 29, 1971

[0025] Glover, U.S. Pat. No. 3,692,306, issued Sep. 19, 1972

[0026] Zebelean, U.S. Pat. No. 4,214,754, issued Jul. 29, 1980

[0027] Schmidt, U.S. Pat. No. 4,511,145, issued Apr. 16, 1985

[0028] Yamada, U.S. Pat. No. 4,535,990, issued Aug. 20, 1985

[0029] Chen, et al., U.S. Pat. No. 4,681,321, issued Jul. 21, 1987

[0030] Kobayashi, U.S. Pat. No. 4,732,389, issued Mar. 22, 1988

[0031] Shearer, U.S. Pat. No. 4,944,515, issued Jul. 31, 1990

[0032] Shiotani, et al., U.S. Pat. No. 4,988,104, issued Jan. 29, 1991

[0033] Duclos, U.S. Pat. No. 5,176,383, issued Jan. 5, 1993

[0034] Atkins, U.S. Pat. No. 5,464,211, issued Nov. 7, 1995

[0035] Rigal, et al., U.S. Pat. No. 5,547,427, issued Aug. 20, 1996

[0036] Lu, U.S. Pat. No. Re. 35,955, reissued Nov. 10, 1998

[0037] Noble, et al., U.S. Pat. No. 5,954,596, issued Sep. 21, 1999

SUMMARY OF THE PRESENT INVENTION

[0038] In accordance with the present invention, a metal club head isdesigned for increased flexure at ball impact including a pleat oralternatively a tongue and groove connection in the perimeter wall thatprovide reduced resistance to face wall expansion at ball impact, andmore energy transfer to the ball, and a face wall reinforcing networkthat increases in height from the perimeter wall to a point near theface wall geometric center.

[0039] The golf club head at ball impact has been extremely difficult toanalyze from a design standpoint because of the peculiar traditionalshape, particularly of the metal wood, the singular point of attachmentof the shaft at the hosel which has no analogy to a vise holding thehead during testing, the bulge and roll of the club face, and thepeculiar effect of the perimeter wall on the face dynamics. The presentinvention does not solve these design problems, but focuses on a systemfor increasing face flexure and energy transfer to the ball.

[0040] This invention or inventions, bifurcates the present solutioninto two parts; the first is a face reinforcing network that increasesin thickness from the perimeter wall to a point near the geometriccenter of the club face according to sound mathematical approximations.The face wall thinning techniques in the prior art, while helpful, donot have face wall thickness variations that optimize face wall flexure.In the present design face wall thickness, or more accurately effectivethickness, increases from the perimeter wall to near the face wallgeometric center by a factor in the range of 3.0 to 7.0 times and doesso geometrically in its more specific definition.

[0041] Effective thickness, as used herein, is the flexurecharacteristic of the present rib reinforcement face compared to a solidface wall of varying thickness without any reinforcing ribs. Thus, usingthe present technique, the present rib design can achieve the same faceflexure pattern as a solid faced club having a face wall thicknessvariation of up to seven fold, without adding the excessive weight ofthat solid face wall.

[0042] In its broadest aspects, some of these principles can be utilizedin solid faced clubs with variable face thickness, such as shown in theKubica, et al., U.S. Pat. Nos. 5,906,549 and 5,954,596. However, thenarrow rib reinforcing network of the present invention permits a fargreater increase in effective face thickness than solid faced clubheads, because it provides greater reinforcement without the trade-offof increased face weight. That is, if in a solid face wall club withface thickness thinning near the perimeter wall, the thickness at theface center were seven times the thickness at the perimeter wall, thethickness at the center would be about 0.434 inches and the club headwould be far overweight. The present invention solves this problem.

[0043] Thus, according to the present invention, the face wall can bevery thin and light, as thin as 0.062 inches when made of a high qualitybeta titanium such as 15 Mo 3-3 hardened. Yet, the ribbing network givesthe same effect as face increase variation of 3 to 7 times in a solidfaced head.

[0044] These principles are based upon the mathematical premise thatface wall stress at ball impact is concentrated in a very small areasurrounding and behind the ball. This is due in part to the outward andinward moments on the face caused by the perimeter wall and thethickness and size of the face wall itself.

[0045] The cross sectional area of the face wall at incrementallyincreasing radii, r₁, r₂, etc. from the center to the perimeterincreases more significantly than previously thought. These areas definethe face wall's ability to resist stress at these radii and thus thelargest sectional area, at the perimeter wall, is capable of handlingthe greatest load. And this is what leads to the conclusion the facewall needs to be dramatically thinner at the perimeter wall than at theface wall center to achieve not only maximum deflection at the face wallcenter, but uniform deflection from the geometric center out to theperimeter wall. This also maximizes the spring effect of the face walland energy transfer to the ball.

[0046] Simple beam theory, discussed below, while helpful, does notproperly analyze club face wall stress because of (1) the torque appliedto the face wall by the perimeter wall and (2) the increasingcross-sectional area of the face wall as the radius about the geometriccenter increases. And while simple calculations indicate the crosssectional area (the area cut by a hole saw around the geometric center)increases linearly; i.e. Kr, as the radius r around the centerincreases, this ignores the moments or torque applied to the perimeterof the face wall by the perimeter wall at ball impact.

[0047] The net effect of these moments caused by the perimeter wall onthe face wall is to strengthen the face wall particularly near theperimeter wall. To compensate for this effect, the present rib networkincreases from zero or near zero near or at the perimeter wall,geometrically at K(X+BX³)¹, to a thickness in one embodiment of about0.125 near the geometric center. (Note the rib height in the drawingsare exaggerated).

[0048] The second design feature of the present invention, claimed inthe above “Related Application”, is a pleat or alternatively tongue andgroove connections between the perimeter wall and the face wall thateach permit the face wall to more easily expand radially (flatten) inthe plane of the face wall. These features are independent of and can beused without the above face wall ribbing. Metal woods normally have facewalls curved in orthogonal planes, the curve in a horizontal plane beingformed on a radius called “bulge”, and the curve in a vertical planebeing found is a radius referred to as “roll”. Face curvature by itselfreduces face wall flexure more than flat faces. Also, the momentscreated by the perimeter wall, which exist in both flat and curved facewalls, resist uniform face deflection and contribute to localized facewall distortion around the ball at impact. If the face wall is permittedto more easily flatten at impact, stresses in the face wall are spreadmore uniformly across the face wall and the face wall deflects moreuniformly from the geometric center to the perimeter wall upon impact.

[0049] It should be understood at this point that effective facethickness variation and pleat or tongue and groove connectors at theperimeter wall are all designed to achieve similar ends; i.e., maximizeface wall deflection. Thus, they can be utilized in club head designindependent of one another, or together, as shown in the drawingsembodiments where they have a cumulative effect toward those ends.

[0050] The perimeter wall pleat or the tongue and groove connections arein fact separate embodiments. In the pleat embodiment, the face wall anda short portion of the perimeter wall are cast in one piece andhardened. The perimeter wall portion has a concave perimeter pleat thatacts as a pair of opposed Bellville springs. As these springs compresson impact, the outer diameter of the springs increases and thus lessensthe resistance the perimeter wall has to face wall expansion. And theBellville springs, upon recovery after compression, deliver energy backto the ball as it leaves the club face wall.

[0051] In the other embodiment, the tongue and groove connection, theface wall floats slightly in the perimeter wall in all directions,permitting face wall expansion and reducing resistance to face walldeflection.

[0052] Other objects and advantages will appear more clearly from thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053]FIG. 1 is a front view of the club head according to the presentinvention;

[0054]FIG. 2 is a top view of the club head according to the presentinvention;

[0055]FIG. 3 is a right side view of the club head according to thepresent invention;

[0056]FIG. 4 is a left side view of the club head according to thepresent invention;

[0057]FIG. 5 is a horizontal mid-section of the front piece of the clubhead;

[0058]FIG. 6 is a vertical mid-section of the front piece of the clubhead;

[0059]FIG. 7 is a rear view of the front of the front piece of the clubhead illustrated in FIGS. 5 and 6;

[0060]FIG. 8 is a left side view of the rear piece of the club headaccording to the present invention;

[0061]FIGS. 9, 10, 11 and 12 are beam theory drawings;

[0062]FIGS. 13 and 14 are beam theory drawings illustrating shear andmoments;

[0063]FIGS. 15 and 16 are disk theory analysis drawings;

[0064]FIGS. 17 and 18 are fragmentary sections illustrating a tongue andgroove embodiment of the present invention, and;

[0065]FIG. 19 is a fragmentary section of a still further tongue andgroove connection embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] It should be understood that the drawings (except FIGS. 18 and19) of the present club head are to scale 1″=1″, within of course thelimits of the patent draftsman, and therefore, dimensions that are notspecifically set forth either as single dimensions, or ranges, may bemeasured on the drawings and as such are within the disclosure of thepresent invention and these dimensions may after the filing of thepresent invention, be added to the disclosure, specification or claimswith the modifier “substantially” without constituting new matter.

[0067] As noted above, both simple single beam technology and circulardisc technology do not have exact analogy to the dynamics of metal golfclubs and particularly metal woods, but do provide a useful comparisonfor experimentation. The bulge and roll of the club face is simulated inFIGS. 9 to 12. In FIGS. 9 and 10, the convex face wall 10 easilyflattens upon impact force P to the flat or concave positions shown inFIG. 10. This occurs when reaction forces F₁ and F₂ act only in avertical direction. What actually happens is depicted in FIGS. 11 and12. The perimeter wall creates moments on the face depicted as M₁ and M₂that resist wall flattening.

[0068] So long as the face wall is convex as shown in both FIGS. 11 and12, the perimeter wall will also exert inward forces F₃ and F₄ on theface wall, resisting flattening to the FIG. 10 position. The result ofthese forces creates the localized depression of the face wall aroundthe golf ball illustrated in FIG. 12 that is responsible for face wallfailure if the designer simply attempts to uniformly thin the face wall.This localized depression represents the condition the present inventioneliminates.

[0069] The perimeter wall, of course, has a positive dynamic effect onthe face wall and energy transfer to the ball. Thus, the appropriatedesign approach is to balance the effects of a FIGS. 9 and 10 designwith the too restrictive effect of the FIGS. 11 and 12 design and tothat end the present inventions are directed.

[0070] A review of beam and disc technology confirms these principles.FIG. 13 shows a single simple beam, centrally loaded that in partanalogizes FIGS. 9 and 10. The shear forces across the beam are constantand the moments at the ends of the beam are zero. The maximum deflectionat the center of beam under a concentrated load at midspan are:$\begin{matrix}{{{\Delta MAX} = \frac{{PL}^{3}}{48E\quad I}}{{where}\quad \begin{matrix}{{P = \quad {force}},} \\{L = \quad {Length}} \\{E = \quad {{Modulus}\quad {of}\quad {Elasticity}}}\end{matrix}}} & {{Eq}.\quad (1)}\end{matrix}$

[0071] Compare this relationship to FIG. 14, which illustrates the sameforce P applied to a single beam centrally when the beam is fixed atboth ends. Note in FIG. 14 the reverse moments M applied to beam. Thissimulates the effect of the perimeter wall on the face wall, althoughnot precisely. The maximum deflection of the beam in this system underthe same load P is defined as: $\begin{matrix}{{\Delta MAX} = \frac{{PL}^{3}}{192E\quad I}} & {{Eq}.\quad (2)}\end{matrix}$

[0072] Somewhat over-simplified, cancelling out the common factors inequations (1) and (2), the non-restrictive system in FIG. 13 has fourtimes the maximum deflection under the same load as the system in FIG.14.

[0073]FIGS. 15 and 16 illustrate circular disc systems that somewhatcomplicate the analysis of simple single beam review. In a single beamthe cross section of the beam stays constant, while in the disc system,the cross sections of the disc, defined at circles around any radius,increase as one moves outwardly from the center or point of theoreticalball impact. This is why the disc analogy is closer to a club head thanthe beam.

[0074] In FIG. 16 (analogous to FIGS. 9, 10 and 13), the maximumdeflection is: $\begin{matrix}{{{\Delta MAX} = \frac{693\quad \Pr^{2}}{400\quad {Et}^{3}}}{{where}\quad \begin{matrix}{E = \quad {{Modulus}\quad {of}\quad {Elasticity}}} \\{P = \quad {Force}} \\{r = \quad {{plate}\quad {radius}}} \\{t = \quad {{plate}\quad {thickness}}}\end{matrix}}} & {{Eq}.\quad (3)}\end{matrix}$

[0075] In FIG. 17 analogous to FIGS. 11, 12, and 14, the maximumdeflection is:${\Delta MAX} = \frac{273W\quad \Pr^{2}}{400\quad {Et}^{3}}$

[0076] Same constants as above.

[0077] Thus, the disc unrestrained in all directions at its perimeterhas a maximum deflection 2.54 times the maximum deflection of the discfixed from movement in all directions at its perimeter. This in partexplains the significant resistive effect of the perimeter wall.

[0078] Referring to the drawings and particularly FIGS. 1 to 8 and 17,18, and 19, a “jumbo” club head 10 is illustrated, preferably entirelyconstructed of a high performance forged or cast beta titanium materialsuch as 15Mo3-3. In the embodiment disclosed in FIGS. 1 to 8, the headis constructed of a forward piece 11 including a face wall 12, and ashort perimeter wall 13, welded to a rear piece 15 illustrated in FIG. 8including a sole plate portion 17, a side and rear wall portion 18, anda crown portion 19. Note that the forward portion 11 carries an integralhosel 20 having a standard shaft receiving bore 21 therein that alsoextends through hosel upper portion 22.

[0079] As noted above, the drawings, as filed, are substantially toscale and the dimensions in some aspects of the present invention areimportant to the performance of the golf club head.

[0080] Firstly, with respect to the size and shape of the face wall 12,and particularly as depicted in FIG. 1, the face wall has a horizontallength F of 4.344 inches, and a vertical height E of 2.344 inches.

[0081] It should be understood that the geometry of the face 12 isdesigned to provide more uniform deflection across the face upon ballimpact, and while the vertical height E in the specific embodiment is2.344 inches, the advantages of the face geometry can be achieved inface walls having a height greater than 1.9 inches. One important aspectof achieving more uniform face wall deflection, according to the presentinvention, is to provide a more circular face which enhances uniformface wall deflection.

[0082] Toward that end the central upper edge 25 and the lower centraledge 26 each have a radius of 3.25 inches although the benefits of thepresent invention can be achieved with these radii in the range of 2.75to 3.50 inches. The upper edges 28 and 29 adjacent central edge portion25 and the lower edge portions 31 and 32 adjacent the lower edge centralportion 26 are tangent to the central portions 25 and 26 and aresubstantially straight to increase the face height at toe portion 33 andheel portion 34 of the face wall.

[0083] The overall volume of the club head 10 is in the range of 370cc., noting that is conventional to quantify club head volume in metricunits even though the dimensions set forth in this specification are ininches. Toward this specific volume, and referring to FIG. 1, theoverall horizontal length of the club head 10 viewed from the front fromthe furthest extent of the toe wall 35 from the heel wall 36 identifiedby the letter G is 4.94 inches, and the overall height of the club fromthe sole portion 17 to the uppermost portion of the crown wall 15identified by the letter D in FIG. 1 is 2.62 inches. Overall club headlength L is 4.156. The hosel 22 has a substantial inset as seen by theratio of A/B.

[0084] As seen in FIGS. 5, 6, and 7, the face wall 12 has a ribbedreinforcing network 38 that promotes the uniform deflection of the facewall from the geometric center to the perimeter wall portion 13. Thatis, the network 38 is designed so there will be a straight linedeflection of the face wall 12 from the geometric center G.C. to theperimeter wall 13 in a fashion similar to the straight line deflectionof the strings in a tennis racket upon ball impact. Note in the plane ofFIG. 5, which is a horizontal plane extending through the geometric axisof the face wall, that the face 12 is curved indicating it has “bulge”,and in the plane of FIG. 6, which is a vertical plane taken through thegeometric center of the face wall, the face wall 12 is also curvedindicating the face wall has “roll”. The curvature of the face wall inthese two orthogonal planes may, for example, be on the order of 15inches. Note also in FIG. 6 that the face wall has a “loft” of 10degrees, and typically loft will vary in the driver club from 6 degreesto about 11 degrees.

[0085] It should be understood at this point that certain aspects of thepresent invention can be applied to fairway woods and iron-type clubs aswell. Irons, however, have no roll or bulge curvatures and hence haveless resistance to face wall deflection assuming equal face thicknessesand size.

[0086] The network 38 is designed to provide a far greater stiffnessvariation from the geometric center to the perimeter wall 13 than can beachieved with variable solid (ribless) face thickness. In variable facethickness designs, which are ribless, face thickness variation can onlyvary by approximately 2.0. That is, the thickness of the face wall nearthe perimeter wall can only be about half the thickness of the face wallat the geometric center G.C. without resulting in excessive face wallweight and excessive overall club head weight. In the present invention,effective face wall thickness with the rib network 38 can compare toface thickness variations of 3.0 to 7.0 in ribless designs withoutadding excessive weight to the head. It should be understood, however,that in the range of 7.0, the network 38 will begin to have excessiveface stiffness, which is contrary to the purpose of the presentinvention so that the preferable operating range for the network 38 iscloser to 3.0 to achieve maximum face deflection.

[0087] The face wall 12, according to the present invention, has auniform thickness between 0.045 inches and 0.070 inches.

[0088] The network 38 is seen to include an annular rib 42 integral withand extending rearwardly from the face wall 12. The annular rib 42 has adepth of between 0.100 to 0.200 inches and a thickness of 0.062 inches,and the rib 42 has a diameter of approximately 0.750 inches. Extendingradially outwardly and integral with both the annular rib 42 and theface wall 12 are eight ribs 43, 44, 45, 46, 47, 48, 49 and 50, spacedapart approximately 45 degrees in the plane of FIG. 7, which is a rearview of the club head body forward piece 11.

[0089] The ribs 45 and 49 (FIG. 6) meet the side of the rib 42 about0.030 inches below the top of the rib 42 and ribs 44, 46, 50 and 48 jointhe side of the rib 42 about 0.020 inches below the top of rib 42.

[0090] Note particularly that near the perimeter wall the ribs 43 to 50have a height of 0 to promote flexure of the face wall, and they havetheir maximum thickness where the ribs join the annular rib 42. Theeffective thickness variation has been determined by comparing thepresent face and network 38 to a plurality of ribless faces having facethickness variations from 3.0 to 7.0. This effective thicknessvariation, defined as the thickness t_(a) at point A near the perimeterwall, and a thickness at a point B near the geometric center, wheret_(b)/t_(a) is at least 3.0 and in the range of 3.0 to 4.0.

[0091] The annular rib 42 may also be elliptical with the major axis ofthe ellipse extending horizontally across the face. The ribs 43 and 50would then be more equal in length and provide more uniform deflectionof the face in both horizontal and vertical directions.

[0092] As noted above, in uniform thickness face walls the crosssectional area of the face about any radius around the geometric centerG.C. increases as the radius about the geometric center increases. It isthis cross sectional area that is proportional to the ability of theface at any given point on the face to resist ball impact stresses onthe face so that at the geometric center G.C., where the radius is 0 andthe section O, the face wall (absent the network 38) is at its weakestpoint in resisting ball impact forces, and at the perimeter wall at 40the section is the greatest and has its greatest resistance to ballimpact and thus the network 38 seeks to weaken the face wall at 40 andto strengthen the face wall strength at the geometric center G.C.,utilizing the network 38. These cross sectional areas, which areeffectively the areas scribed by hole saws centered about the geometriccenter G.C., increase linearly from the geometric center to near theperimeter wall. However, this analysis neglects the effect of theperimeter wall on the face wall, which is, to provide moments on theface wall tending to maintain the curvature of the face wall 12. Tocompensate for the effect of the perimeter wall on the face wall, theribs 43 to 50, rather than being straight in configuration to match thelinear variation in face wall cross sections moving outwardly from thegeometric center G.C., are instead curved to further weaken the facewall moving radially outwardly from the geometric center to compensatefor the moments acting on the face wall by the perimeter walls aroundthe face wall.

[0093] Face wall deflection, according to the present invention, isfurther enhanced by a pleat 54 illustrated in FIGS. 1 to 7, and anelastomeric tongue and groove section illustrated in FIGS. 17, 18 and19. As noted above, the ability of the face wall to flatten upon ballimpact is impeded by the perimeter wall, which in accordance with theanalysis in FIGS. 11, 12, 14, and 16, provides inward forces on the facewall 12 that inhibit the flattening of the face wall upon ball impact.The pleat 54 and the tongue and groove connection 55 reduce the inwardforces acting on the face wall by the perimeter walls.

[0094] The pleat 54, as seen in FIGS. 2 to 8, is formed in the forwardpart 13 illustrated in FIG. 7, and extends completely around the facewall except at the hosel 22. The perimeter wall at the hosel 22, as seenin FIG. 2, has a slot 56 that connects pleat portion 54 a and pleatportion 54 b.

[0095] As seen in FIGS. 5 and 6, the pleat 54 is defined by perimeterwall portion 59 and perimeter wall portion 60 that are generallyV-shaped in configuration. Wall portion 59 has an angle of approximately55 to 60 degrees with respect to a vertical plane noted in FIG. 5, whilewall portion 60 has an angle of about 5 to 10 degrees with respect tothat same parallel plane. It should be understood, however, that theangles of wall portions 59 and 60 vary to accommodate the uniquegeometry of the crown wall, side walls, and sole plate of the particularclub head under consideration.

[0096] The walls 59 and 60 are in effect Bellville springs that collapseslightly upon ball impact and permit face wall perimeter edge in theplane 61 to move outwardly upon ball impact as the pleat 54 collapsesslightly in accordance with well known Bellville spring geometry. Itshould also be noted that the pleat 54 as it expands as the ball leavesthe face 12, releases its stored energy to the ball enhancing ball exitvelocity.

[0097] The slot 56 weakens the face slightly at the hosel 22 to preventthe hosel from rigidifying the face excessively at this point. The pleatmay be covered by rings coplanar with the outer walls of the club headfor aesthetics.

[0098] As seen in FIGS. 17 and 18, the elastomeric tongue and grooveconnection 55 includes a rectangular perimeter recess 66 in theperimeter of the face wall 12 a, and a perimeter tongue 67 integrallyformed on an annular bezel 68 welded to an annular recess 69 in theforward edge of perimeter wall 70. A U-shaped elastomeric ring 72 ismounted in recess 66 and around the tongue 67. Ring 72 has a durometerin the range of 50 to 90 Shore A. This elastomeric connection permitsthe face wall to flatten more easily upon impact as the face wall 12 atwists about the tongue 67 in the plane of FIG. 18. In addition tofacilitating the twisting of the face wall 12 a as it flattens, theelastomeric connection 55 also permits radial expansion of the face wall12 a, which of course tends to occur as the face wall flattens from itsroll and bulge unloaded configuration.

[0099] An alternative elastomeric connection 76 is illustrated in FIG.19 where tongue 77 is formed on the face wall and groove 78 is formed onbezel 79.

1. A golf club head, comprising: a face wall, a perimeter wallsurrounding at least a major portion of the face wall and attached to aperimeter of the face wall, said club head having a shaft receivinghosel therein, said face wall having a geometric center and extendingoutwardly from that center 360 degrees toward the perimeter wall, saidface wall increasing in effective thickness from a point A (t_(a)) nearthe perimeter wall toward the geometric center to an effective thickness(t_(b)) at a point B near the geometric center where t_(b)/t_(a) is atleast 3.0.
 2. A golf club head as defined in claim 1, whereint_(b)/t_(a) is in the range of about 3.0 to 7.0.
 3. A golf club head,comprising: a face wall, a perimeter wall surrounding at least a majorportion of the face wall and attached to a perimeter of the face wall,said club head having a shaft receiving hosel therein, said face wallhaving a geometric center and extends outwardly from that center 360degrees toward the perimeter wall, said face wall increasing ineffective thickness from a point A (t_(a)) near the perimeter wall in ahorizontal direction toward the geometric center to an effectivethickness t_(b) at a point B near the geometric center, where theeffective thickness (t) of the face wall increases at a constant rate orhigher from point A to point B.
 4. A golf club head, comprising: a facewall, a perimeter wall surrounding at least a major portion of the facewall and attached to a perimeter of the face wall, said club head havinga shaft receiving hosel therein, said face wall having a geometriccenter and extending outwardly from that center 360 degrees toward theperimeter wall, said face wall having a substantially uniform thickness,and means for increasing the effective thickness of the face wall fromnear the perimeter wall to a point near the geometric center including arib network formed integrally with the face wall, said rib networkincreasing thickness from near the perimeter wall to a point near thegeometric center.
 5. A golf club head as defined in claim 4, wherein therib network includes a generally annular or elliptical rib formedintegrally with the face wall near the geometric center of the face walland extending rearwardly therefrom a substantial distance.
 6. A golfclub head as defined in claims 4 or 5, wherein the rib network includesa plurality of ribs extending from about the geometric center generallyradially toward the perimeter wall.
 7. A golf club head as defined inclaim 6, wherein the plurality of ribs increase in height from near theperimeter wall to a point near the geometric center at a constant rateor higher.
 8. A wood club head, comprising: a face wall having a loftand being curved in a horizontal plane defining bulge and curved in avertical plane defining roll, a perimeter wall surrounding and enclosingthe face wall, said face wall having a substantially uniform thickness,and means for increasing the effective thickness of the face wall fromnear the perimeter wall to a point near the geometric center including arib network formed integrally with the face wall with at least aplurality of the ribs extending from the point near the geometric centerto the perimeter wall, said plurality of ribs having an increasingthickness from near the perimeter wall to the point near the geometriccenter.
 9. A wood club head as defined in claim 8, wherein the ribnetwork includes a generally annular or elliptical rib formed integrallywith the face wall and extending rearwardly therefrom a substantialdistance, said annular or elliptical rib having a center approximatelynear the geometric center of the club face, the plurality of ribsextending integrally from the annular or elliptical rib generallyradially toward the perimeter wall.
 10. A wood club head as defined inclaim 8, wherein the plurality of ribs increase in height from near theperimeter wall to the point near the geometric center at a constant rateor higher.
 11. A wood club head as defined in claim 10, wherein the ribsincrease in height from near the perimeter wall to the point near thegeometric center and are exponentially curved.